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examples/triangles: Draw polygons

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This commit is contained in:
Hajime Hoshi 2018-08-14 01:49:45 +09:00
parent 5032546238
commit 1b8cad4e1d
1 changed files with 36 additions and 10 deletions
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46
examples/triangles/main.go
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@ -24,6 +24,7 @@ import (
"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
"github.com/hajimehoshi/ebiten/inpututil"
)
const (
@ -41,19 +42,21 @@ func init() {
var (
vertices []ebiten.Vertex
indices []uint16
numVerticesToDraw = 10
prevNumVerticesToDraw = 0
)
func init() {
func genVertices(num int) []ebiten.Vertex {
const (
num = 120
centerX = screenWidth / 2
centerY = screenHeight / 2
r = 160
)
vs := []ebiten.Vertex{}
for i := 0; i < num; i++ {
theta := float64(i) / num * 2 * math.Pi
theta := float64(i) / float64(num) * 2 * math.Pi
cr := float32(0)
cg := float32(0)
cb := float32(0)
@ -75,7 +78,7 @@ func init() {
if 0 <= i && i < num/3 {
cb = 2 - 2*float32(i)/float32(num/3)
}
vertices = append(vertices, ebiten.Vertex{
vs = append(vs, ebiten.Vertex{
DstX: float32(r*math.Cos(theta)) + centerX,
DstY: float32(r*math.Sin(theta)) + centerY,
SrcX: 0,
@ -87,7 +90,7 @@ func init() {
})
}
vertices = append(vertices, ebiten.Vertex{
vs = append(vs, ebiten.Vertex{
DstX: centerX,
DstY: centerY,
SrcX: 0,
@ -97,19 +100,42 @@ func init() {
ColorB: 1,
ColorA: 1,
})
for i := 0; i < num; i++ {
indices = append(indices, uint16(i), uint16(i+1)%num, num)
}
return vs
}
func update(screen *ebiten.Image) error {
if inpututil.IsKeyJustPressed(ebiten.KeyLeft) {
numVerticesToDraw--
if numVerticesToDraw < 1 {
numVerticesToDraw = 1
}
}
if inpututil.IsKeyJustPressed(ebiten.KeyRight) {
numVerticesToDraw++
if numVerticesToDraw > 120 {
numVerticesToDraw = 120
}
}
if prevNumVerticesToDraw != numVerticesToDraw || len(vertices) == 0 {
vertices = genVertices(numVerticesToDraw)
prevNumVerticesToDraw = numVerticesToDraw
}
if ebiten.IsDrawingSkipped() {
return nil
}
op := &ebiten.DrawTrianglesOptions{}
indices := []uint16{}
for i := 0; i < numVerticesToDraw; i++ {
indices = append(indices, uint16(i), uint16(i+1)%uint16(numVerticesToDraw), uint16(numVerticesToDraw))
}
screen.DrawTriangles(vertices, indices, emptyImage, op)
ebitenutil.DebugPrint(screen, fmt.Sprintf("TPS: %0.2f", ebiten.CurrentTPS()))
msg := fmt.Sprintf("TPS: %0.2f\nVertices: %d\nPress <- or -> to change the number of the vertices", ebiten.CurrentTPS(), numVerticesToDraw)
ebitenutil.DebugPrint(screen, msg)
return nil
}